Long Line


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Long Line

 

an electrical line formed by two parallel current conductors whose length is greater than the wavelength of the electromagnetic oscillations being transmitted and that are separated by a distance considerably less than the wavelength. A long line is a system with distributed constants (parameters), since every element of its length has at the same time certain values for the inductance L and resistance R of the wires and capacitance C and conductance G between them. The main characteristics of a long line, the characteristic impedance W and the propagation velocity v of electromagnetic waves along it, are governed by these parameters. The instantaneous values for the strength and voltage of an alternating current at any point on a long line are mathematically related by the so-called telegraph equations. A long line is called homogeneous if its parameters are constant over its entire length; if there are no electrical losses in it—that is, if R’ = G = 0 (usually at radio frequencies)—then Long Line and Long Line.

In the general case, the input impedance of a long line is complex in nature (it includes resistive and reactive components) and is a function of the length and the type of electrical load at its end (output). The input impedance of an infinitely long line is equal to W. For the maximum transmission of power from a source to the line its input impedance should be resistive and equal to the internal resistance of the source—that is, it must be matched. A long line can operate in three modes: the traveling-wave mode, in which the transmitted power is completely absorbed by the load (the load impedance is resistive and equal to W); the standing-wave mode, in which the transmitted power is completely reflected from the end of the line toward the source (a long line that is short-circuited or open-circuited at the end); and the intermediate mode (the load impedance is complex and is not equal to W).

Long lines are used to transmit information in long-distance telegraph and telephone communications systems, in television, and in radar, as well as to transmit power over wire for great distances.

REFERENCES

Garnovskii, N. N. Teoreticheskie osnovy elektroprovodnoi sviazi, part 2. Moscow, 1959.
Gonorovskii, I. S. Radiotekhnicheskie tsepi i signaly, part 2. Moscow, 1967.
IU. B. LIUBCHENKO

Long Line

 

gear used for catching mainly predatory fish, a type of hooked tackle. A long line consists of a strong rope to which shorter lines with baited hooks are attached.

References in classic literature ?
Until the whale fishery rounded Cape Horn, no commerce but colonial, scarcely any intercourse but colonial, was carried on between Europe and the long line of the opulent Spanish provinces on the Pacific coast.
The steam ploughs had, however, kept the railroad open, and the evening train which connects the long line of coal-mining and iron-working settlements was slowly groaning its way up the steep gradients which lead from Stagville on the plain to Vermissa, the central township which lies at the head of Vermissa Valley.
The long line of savages advanced a few steps more, their spears poised above their heads, their half-naked forms showing more distinctly as they peered forward through the grey gloom, savage and ferocious.
Came the long line of stalled street-cars, the crowd, the police holding it back, the two ambulances drawn up and waiting their freight, and the young policeman, whose beat it was, white and shaken, greeting him with: "It's horrible, man.
A man who had formed one of the long line of passengers, leaning over the rail, watching the tug since it had come into sight, now turned away and walked briskly to the steps leading to the bridge.
There was a little murmur from the shore, where the fishermen stood in a long line.
THE roarings that had stretched in a long line of sound across the face of the forest began to grow intermittent and weaker.
The trappers proceed across the prairie in a long line; or sometimes three parallel lines, sufficiently distant from each other to prevent the packs from interfering.
She stood watching the fair woman walk down the long line of galleries with the grace and majesty which queens are sometimes supposed to possess.
The Soldier now returned with a long line and tied all three firmly together, also lashing them to the body of the Saw-Horse; so there seemed little danger of their tumbling off.
The uprising movement has been interrupted by at least eight long periods of rest, during which the sea ate, deeply back into the land, forming at successive levels the long lines of cliffs, or escarpments, which separate the different plains as they rise like steps one behind the other.
They entered; behind a glass window, by the light of the cardinal's lantern, which had been placed on the floor in the midst of the gallery, they saw the orange and pomegranate trees of the Castle of Rueil, in long lines, forming one great alley and two smaller side alleys.